Question

尝试以特定格式准备此数据

import pandas as pd

voting = pd.read_json("GE2000.json")
voting.set_index(['county_fips','candidate_name','pty','vote_pct'],inplace=True)

print(voting)

然后返回

                                            vote
county_fips candidate_name  pty vote_pct
2000        Howard Phillips CS  0            596
            John Hagelin    NL  0            919
            Harry Browne    LB  1           2636
            George W. Bush  R   59        167398
            Al Gore         D   28         79004
1001        Howard Phillips I   0              9
            John Hagelin    I   0              5
            Harry Browne    LB  0             51
            George W. Bush  R   70         11993
            Al Gore         D   29          4942

在此之后，我想对vote_pct进行排序并抓住最大的，就像这样（我已经尝试过sort_values，sort_index等，并且不能让它产生所需的输出）

                                            vote
county_fips candidate_name  pty vote_pct
2000        George W. Bush  R   59        167398
1001        George W. Bush  R   70         11993

这是示例数据

[

  {
    "office" : "PRESIDENT",
    "county_name" : "Alaska",
    "vote_pct" : "0",
    "county_fips" : "2000",
    "pty" : "CS",
    "candidate_name" : "Howard Phillips",
  },
  {
    "office" : "PRESIDENT",
    "county_name" : "Alaska",
    "vote_pct" : "0",
    "county_fips" : "2000",
    "pty" : "NL",
    "candidate_name" : "John Hagelin",
  }
]

该数据继续

Answer 1

在执行groupby之前，您可以使用apply和set_index获取最大值，然后再设置索引。这允许您在列上而不是在索引上使用groupby（这很奇怪）：

voting = pd.read_json("GE2000.json")

get_largest_vote_pct = lambda row: row[row.vote_pct == row.vote_pct.max()]

largest = voting.groupby('county_fips').apply(get_largest_vote_pct)

largest.set_index(['county_fips','candidate_name','pty','vote_pct'],inplace=True) 

print(largest)

                                           vote
county_fips candidate_name pty vote_pct        
1001        George W. Bush R   70         11993
2000        George W. Bush R   59        167398

Answer 2

您可以使用groupby例如voting.groupby('county_fips')['candidate_name'].max()。

这里还有更详细的答案： Python : Getting the Row which has the max value in groups using groupby

设置索引排序特定列pandas

2 个答案: